Disclosed herein is a wakefulness-maintenance apparatus and, more specifically, a wakefulness-maintenance apparatus that applies a stimulus to a seated person on a vehicle seat.
Securing the safety in vehicle travel is closely related to the health condition of a driver. From this, it has been proposed that the physical condition of the driver is monitored, and the driver is called to attention by an alarm, a warning light, or the like, when an abnormal condition is detected.
For example, Japanese Patent Document No. H05-330360 A (“the '360 Document”) discloses a doze prevention device that vibrates a vehicle seat at a frequency in a range which does not give discomfort to a seated person in order to prevent dozing. The frequency is specifically set to 40 Hz-50 Hz. The vibration stimulus by this device gives less unpleasant feeling and produces a wakefulness effect.
Moreover, for example, Japanese Patent Document No. H11-78591 A (“the '591 Document”) discloses a device that applies a vibration stimulus having an intensity depending on the sensitivity of a seated person to the seated person by a vibrating motor if dozing of the seated person is recognized. This device produces a high wakefulness effect without being affected by the difference of the sensitivity of the seated person to the vibration stimulus.
Further, for example, Japanese Patent Document No. 2012-136134 A (“the '134 Document”) discloses a device that maintains the wakefulness of a seated person without giving discomfort to the seated person by applying a vibration synchronous with the heartbeat of the seated person to the seated person.
Although there are frequencies which are perceived to be unpleasant, the device disclosed in (“the '360 Document”) applies a vibration stimulus at a predefined frequency of 40 Hz-50 Hz to minimize the number of seated persons from perceiving the applied frequency as being unpleasant.
Moreover, as the device disclosed in (“the '591 Document”), even if adjustment of the vibration intensity of the vibrating motor can produce a high wakefulness effect without being affected by the difference of the sensitivity of the seated person, it has previously proven difficult to remove discomfort due to the vibration.
Moreover, as the device disclosed in (“the '134 Document”), in a case where a stimulus synchronous with the heartbeat of a seated person is applied, it is possible to prevent discomfort to the seated person. However, in a case where a similar stimulus is applied multiple times in a short time period, as represented by the drowsiness level of the seated person on vertical axis and the time on horizontal axis shown in a graph of FIG. 12, there has been a tendency that the seated person becomes accustomed to the stimulus.
Various embodiments disclosed herein consider such problems, and an object thereof is to provide a wakefulness-maintenance apparatus capable of applying a stimulus, which does not discomfort most seated persons, to a seated person, and effectively maintaining the wakefulness of the seated person.